Whenever I try the installer, it stops with an error message stating that sdb has BIOS RAID metadata on it so it'll just get ignored. Try as I might, I can't get rid of this. If I disable the SATA controller on the motherboard then the error goes away, but so does sdb, so that's not a solution.

I've started the live DVD with the dodmraid kernel option.

I initially thought that the onboard SATA controller would do the RAID work, but after doing an initial install I found only sda had anything on it, so it's obvious I'm going to have to go the fake RAID route on this one.

Does anyone know how to nuke sdb so it gets included by the installer?

I think it would be smart first install on one drive and then migrate to a RAID1 set ...

But I do not recommend to use the FakeRaid method!The hardware Raid controller (Fakeraid SATA or IDE) built on motherbard are a poor version of software RAID LVM, IMHO.The performances are almost always low and not comparable to those of a "real" dedicated RAID hardware controller (SCSI or SAS).And last usually needed (but not really true) only when Redmond and Linux OSes shared over the Raid Volume.

So if you use only Linux OS, I advise you to disable the raid from bios and use software RAID with kernel device mapper...I think the Raid software for Redmond OSes is only supported on Windows Server family (but not shure).

First create two raid partitions (one for each HDD) and then enable the RAID set in mode 1.mdadm --create /dev/md0 --level=mirror --raid-devices=2 /dev/sda1 /dev/sdb1

I did, but by taking an alternate route: I gave up using the Sabayon installer and just installed a full Gentoo system instead. No matter what I did with Sabayon, I couldn't get it to work with this motherboard and RAID, and I'd run out of time.